Sewage treatment plants

Contents

1. Source Data

2. Choice of waste water outlet and treatment plant location

3. Design costs and wastewater concentrations

• 3.1 Determination of estimated waste water flow rates

• 3.2 Determination of wastewater concentrations

• 3.3 Determination of the given number of inhabitants

4. Required degree of wastewater treatment for water runoff

• 4.1 Determination of mixing ratio of wastewater with water of the reservoir

• 4.2 Determination of the required degree of cleaning

5. Choice of Waste Water Treatment Method and Treatment Plant Flow Diagram

6. Main sewage pump station

7. Mechanical wastewater treatment facilities

• 7.1 Grids

• 7.2 Horizontal sand heads

• 7.3 Primary radial sumps

8. Biological Waste Water Treatment Facilities

• 8.1 Aerotanks - displacers with regenerators

• 8.2 Secondary sumps

9. Biologically treated waste water post-treatment facilities

10. Waste water decontamination and discharge facilities

• 10.1 Decontamination of clarified water

• 10.2 Mixing and water measuring devices

• 10.3 Contact tank

11. Blower station

12. Sedimentation treatment facilities

• 12.1 Low seal

• 12.2 Metantenki

• 12.3 Washing and compaction of fermented sludge

• 12.4 Centrifuges

• 12.5 Storage sites. Sludge sites

13. Feasibility Study

List of literature

1. Initial data.

Sewage treatment plants are designed for a city located in the Kharkov region of Ukraine.

The city has two residential districts with expenses of 58842 m3/day and 28400 m3/day; machine-building plant with production waste water flow rate of 300 m3/day and bakery with production waste water flow rate of 280 m3/day. Expenses for household drains of enterprises for public buildings are given in Table No. 1. The estimated daily flow rate is 91104.9 m3/day, the maximum hour is 6133.9 m3/hour .

The waste water of the meat processing plant has concentrations of contamination by suspended substances of 1000 mg/l and BPKPpoln - 800 mg/l. According to the rules of wastewater discharge into the city network, wastewater is treated at factory local treatment facilities up to 500 mg/l for suspended substances and BPC full..

Waste water of the machine-building plant has concentrations of contaminants by suspended substances of 130 mg/l and BPKPoln - 100 mg/l.

Waste water is discharged into the reservoir.

Characteristics of the reservoir:

type of water use -I sb;

minimum water flow of 2.0 m3/s;

average flow rate with minimum water flow of 0.4 m/s;

depth of the reservoir at GHV: 5 m - maximum, 3 - average;

the width of the river: 20 m - in the low water, 65 m - in the flood;

concentration, mg/l:

• dissolved oxygen (summer/winter) - 7/8.4;

• suspended substances - 10;

• BPKpoln - 3;

the distance from the waste water outlet to the water use point: 8.5 km in the forward, 8.2 km in a straight line.

Sludge treatment method: fermentation of sludge and sludge in methantenes in mesophilic mode and dehydration on centrifuges

2. Choice of waste water outlet and treatment plant location.

The site for treatment facilities should be located on the leeward side in relation to residential buildings and necessarily downstream of the city. High-altitude arrangement of treatment facilities on the selected site shall ensure gravity movement of waste water, and the site itself shall not be flooded with floods .

Treatment facilities from the boundaries of residential buildings should be separated by sanitary protection zones, the size of the zones depends on the design flow rate, the required degree of purification and the composition of the structures.

The composition of treatment facilities depends on the throughput capacity, the required quality of the degree of waste water treatment, the chosen method of treatment and use of sediments, as well as on local conditions and is justified by the corresponding feasibility calculations.

The mutual location of the facilities should take into account the possibility of construction of a waste water treatment complex in queues and expansion. Structures and buildings should be located possibly more compact. The distance between individual structures should provide the possibility of laying technological communications, arrangement of access roads and driveways, required fire and sanitary breaks. In addition, it is necessary to take into account the width of laying slopes of the layout.

The laying of technological and engineering communications should be carried out in shorter directions, compact, advantage along the driveways. Air ducts and heat networks are recommended to be laid on low supports with a device for transitions above or under driveways. The designed driveways shall ensure the movement of goods in both directions in one row. At the final stage of the development of the general plan, the outlines of green spaces should be indicated.

When designing treatment facilities, it should be possible to block them and a reasonable, optimal number of esputation units.

During the design and construction of treatment facilities, devices are provided for the uniform distribution of waste water between individual facilities or their groups, devices for the emptying of facilities for the duration of repair or preventive technological work. It is necessary to provide construction of bypass pipelines or channels for emergency waste water discharge, installation of instruments and devices for measuring the amount of waste water, sludge and active sludge, air flow rate, steam and gas.

To ensure gravity movement of water through treatment facilities, the elevation of the water surface in the supply channel near the receiving chamber should exceed the elevation of water in the reservoir, at a high water horizon in the waste water receiver. This value should be sufficient to compensate for all head losses along the path of water movement through the structures, taking into account a reserve of 1-1.5 m, which is necessary to ensure the free flow of water from the outlet tip to the reservoir. The normal operation of the treatment plant depends to a large extent on the correct determination of hydraulic losses at the inlet of waste water from the facilities, when it flows in channels or pipelines, distribution devices, etc.

To simplify the preliminary construction of the high-rise arrangement of structures, with the exception of grates, head losses are accepted: half at the entrance to the structure, the second half at the exit from it.

The total amount of head loss at the treatment plants depends on the compactness of the location, that is, on the amount of gaps between them and the length of the supply trays. Approximately it can be taken with mechanical and physicochemical methods of purification -2-3 m, with biochemical methods - 4-6 m (for aerotanks) and 410 m (for biofilters, depending on the height of the layer of loading material).

For more accurate determination of water level elevations at various points of the station, local resistance losses must be taken into account: at the entrance of water from the structure, in measuring devices and mixers, at points of turns, narrows or extensions of channels, etc.

After the treatment facilities are placed on the general plan, I denote the points for calculation (from the places of change of water flow, channel or structure). The calculation direction is selected along the longest path.

To determine the mutual high-altitude location of individual structures of the treatment plant, simultaneously with the development of the master plan, profiles of water, sediment and sludge movement are built (profiles "by water" and "by sludge").

The profile "on water" is a detailed section along the structures along the longest path of water movement from the supply channel to the outlet into the reservoir. The "silt" profile starts from the primary settling tanks and is located at the sediment dewatering facilities.

3. Design costs and wastewater concentrations.

3.1 Determination of estimated waste water flow rates.

The estimated waste water flow rate is the flow rate for which the sewage treatment facilities are calculated.

The city has two residential districts with expenses: the 1st district - 58842 m3/day, the degree of improvement of the VKC and the III district - 28400 m3sutki, the degree of improvement of the VKM; machine-building plant with a production waste water flow rate of 300 m3/day and a meat processing plant with a production waste water flow rate of 280 m3/day.. The estimated daily flow rate is 91104.9 m3/day, the maximum hour is 6133.9 m3/day .

5. Selection of waste water treatment method and POC flow chart.

Based on the above calculations, waste water treated to a suspended content of 10.24 mg/l and BPC full of 13.7 mg/l can be discharged into the river.

At present, when the problem of protecting water resources from pollution by wastewater from cities and industrial enterprises is very acute, the most effective and reliable method of treating urban wastewater is complete biological treatment.

Modern requirements of sanitary and fisheries management methods are such that in treated wastewater the concentration of suspended substances and BPC should not exceed 3-5 mg/l. In these cases, deep treatment or post-treatment of wastewater is envisaged.

Wastewater treatment methods are divided into mechanical, chemical and biological.

With the mechanical method, settling and popping substances are isolated from waste water. During this purification, 60-80% of insoluble contaminants can be retained. To detain large substances, grates and nets are provided. For the deposition of solid particles of mineral origin, sandwiches installed after grates are used.

Settling tanks are the main and most common type of treatment facilities built for the purpose of mechanical treatment of waste water. Insoluble suspended substances of both organic and mineral origin precipitate in them.

Biological treatment methods are used to extract from wastewater the smallest suspensions that do not settle in settling tanks, as well as colloids and dissolved substances. As a result of aerobic biochemical processes taking place in structures of this type, organic substances are mineralized. Biological treatment is the second stage of wastewater treatment.

Biological wastewater treatment facilities are divided into two groups: in the first, treatment is carried out in conditions close to natural; second, cleaning is carried out in filters of various types and aerotanks.

This project provides for complete biological treatment of waste water with post-treatment on granular filters.

Even with complete biological treatment, it is completely impossible to eliminate bacterial pollution of wastewater. Finally, bacteria can be destroyed only by disinfection. At the current level of the economic situation of the national economy, chlorine is used to disinfect treated wastewater.

Anaerobically fermented precipitate in mesophilic mode must be disinfected. The obtained sediment is sent for dehydration on centrifuges and drying at storage sites.

Sand falling in sandwiches is removed to sand sites, where it is dried and then exported.

6. Main sewage pump station.

For the supply of municipal wastewater to the KOS, the construction of the KOS of the first category is provided. The station is provided with a semi-deep: in the underground part - a machine room and a reception chamber, in the above-ground - an electric panel, administrative rooms, workshops.

Pumps and pressure headers are selected according to the maximum hourly inflow qmax = 6133.9 m3/h (1703.9 l/s or 1.7 m3/s). We lay pressure headers in two threads [1]. In the event of an accident on one of the headers, the other should pass 100% of the design flow. From the Shevelev tables, we determine the diameter of the pressure manifold.

Headers from reinforced concrete pressure pipes with diameter of 1200 mm GOST 1695378, speed of 1.1 m/s, 1000i = 0.86 m are accepted for laying.

Required head of LCS pumps is determined by formula:

Np = (Z pc - Zp) + 1,2. hnv + hnas + hc.isl, m

(74.2 - 65) + 1.2.2 + 3 + 1.5 = 16.1 m

Z pc, m - elevation of water level in KOS receiving chamber;

Znr, m- elevation of the bottom of the ISS receiving tank;,

hnv - head reserve for liquid discharge from pipelines, 2 m is accepted

Pump station is received with combined arrangement of receiving tank and engine room, head losses inside station pipelines are taken equal to hns = 3.0m.

Determine head losses in external pressure pipelines.

4 operating and 2 standby pumps of EMU FK 40.75Z grade are accepted for installation, with the following parameters Q = 1500 m3/h; H = 20 m, N = 125 kW; weight 1300 kg; engine of FK42.16/46 grade.

The capacity of the receiving tank of the pump station is determined depending on the inflow of waste water, the capacity of the pumps, the permissible frequency of the pumps, but not less than 5-minute maximum capacity of one pump.

In case of automatic switching on of electrical equipment and pumps driven by motors with N 50 kW, the permissible switching on frequency is not more than 3 times per hour. The receiving tank is provided with devices for agitating the sediment and washing the tank, the slope of the bottom of the tank to the pit 0.2.

We determine the minimum allowable capacity of the tank per hour of minimum inflow, which should be at least 5 minutes maximum capacity of one pump.

To receive waste water from pressure headers in front of treatment facilities, a receiving chamber is arranged, made in the form of a reinforced concrete well with dimensions of 3500 x 2500 mm.

7. Mechanical wastewater treatment facilities.

Mechanical cleaning is carried out to extract insoluble contaminants from waste water located in it mechanically. To deter large contaminants and partially suspended substances, screening through grates and sieves is used. The separation of suspended particles of mineral origin, mainly sand, from wastewater is carried out by precipitation in sandwiches. The extraction of the bulk of the finer suspension, mainly organic, from the waste water is carried out in settling tanks.

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